This invention is generally directed to the field of collar making and, more specifically, to collars formed of sheet metal such as used in heating and ventilating systems. In such systems, heated or cooled air is carried by ducts to which pipes are connected at various positions for directing the air to individual rooms or areas. Collars are attached at holes formed in the duct wall and pipe sections are then attached to the collar.
In one collar design, one corner of a rectangular strip of sheet metal is notched on a stamping machine. The stamped strips of sheet metal are then taken to a conventional collar making machine for fabrication. The collar making machine forms a channel along the side edge of the strip having the notch, forms the strip into a circular configuration, and crimps the other side edge of the strip. The ends of the strip overlap each other and are secured together by conventional means such as spotwelding. Thus, what was originally the sides of the strip have now become the ends of a circular collar. The notch provides an opening in the outer wall of the channel which permits the channel end of the collar to be screwed into a hole in the duct wall which is dimensioned to receive the channel. The crimped end of the collar has a decreased diameter which allows a pipe section to be slipped over this end thereby facilitating attachment of the pipe to the collar. Producing such collars from strips of sheet metal which have been previously notched is well known.